The present invention relates to a control apparatus for controlling the operation of an outboard marine engine. More particularly, it relates to an engine control apparatus which is able to adjust or modify engine control parameters in response to a three-dimensional attitude of an outboard engine, which is mounted on a boat, to prevent the boat from deviating from a predetermined cruising course for improved cruising performance.
FIG. 6 schematically illustrates a typical example of an outboard marine engine mounted on a boat. In this figure, the engine 1 in the form of an internal combustion engine for outboard use is disposed outside a boat hull 3 at the stern thereof and pivotally mounted to the boat hull 3 through a mounting bracket 1a so that it is pivotable around a vertical pivot axis (Z-axis) as well as an athwart pivot axis P1 (Y-axis) which extends horizontally athwart of the boat hull 3. Upon acceleration of the engine 1, it is caused under an acceleration force to pivot or incline around the athwart pivot axis P1 (Y-axis) at an attitude angle or angle of tilt .THETA..sub.1 (i.e., so-called "trim angle") from a normal or vertical position (i.e., a reference or vertical line) which the engine 1 takes in a steady-state operation. The engine 1 is steered to turn around the vertical pivot axis (Z-axis) by an operator through an unillustrated steering and throttle arm lever. A propulsion screw 2 is disposed under water and operatively connected with the engine 1 so that it is thereby driven to rotate, generating a propulsion force.
FIG. 7 shows in block form the general construction of a conventional engine control apparatus for controlling the outboard engine 1 of FIG. 6. In this figure, a rotational speed sensor 4 mounted on a camshaft or crankshaft (not illustrated) of the engine 1 generates a crank angle signal R representative of a reference crankshaft position in synchronization with the rotation of the unillustrated crankshaft for sensing the rotational speed or the number of revolutions per minutes of the engine 1. A gear position sensor 5 senses the gear position of a transmission (not shown) of the engine 1 and generates a corresponding gear position signal G. A controller 6 receives output signals from various sensors indicative of various engine operating conditions such as the degree of throttle opening, the intake pressure in an intake manifold, etc., including the output signals R, G from the rotational speed sensor 4 and the gear position sensor 5, and generates a drive signal A for controlling various engine control parameters on the basis of these output signals. An actuator means 7 is operatively connected to receive the drive signal A from the controller 6 so that it is driven to operate by the controller 6 through the drive signal A. The actuator means 7 controls various driving and control elements or devices such as a fuel pump, an ignition coil, a throttle valve, a starter motor and the like associated with the engine 1.
Next, the operation of the above-described conventional engine control apparatus will be described in detail while referring to FIGS. 6 and 7. First, the controller 6 generates a drive signal A based on the output signals from the various sensors including the rotational speed signal R, the gear position signal G, the reference crank signal and the like representative of various engine operating conditions, for controlling the actuator means 7 (e.g., for controlling a fuel pump, an ignition coil, a throttle valve, etc.) as well as calculating and controlling operational timings thereof such as fuel supply or injection timing, ignition timing, etc. As a result of such calculations, the controller 6 generates an appropriate drive signal A so that the actuator 7 is thereby operated to properly control engine control parameters such as the flow rate of intake air sucked into the engine 1, the amount of fuel supplied to the engine 1, the ignition timing and the like, thus providing a desired number of revolutions per minute of the engine 1.
In this connection, since the engine load varies in accordance with a change in the three-dimensional attitude of the engine 1, control performed by the actuator means 7 on the engine control parameters through the drive signal A, which is calculated and generated by the controller 6 on the basis of various sensor signals without taking account of the engine load, becomes improper or unsuitable, so the boat often deviates from an intended cruising course such as during acceleration or turning motion thereof, thus reducing or impairing the cruising performance. In particular, in case of acceleration on a curved course, not only the trim angle .theta..sub.1 but also other angles of inclination (bank and yaw angles) of the boat hull 3 with respect to three reference axes (i.e., the vertical Z-axis, the longitudinal X-axis extending longitudinally of the boat hull 3 and perpendicularly to the vertical Z-axis, and the athwart Y-axis extending athwart of the boat hull 3 and perpendicularly to the vertical Z-axis and the longitudinal X-axis) become greater, resulting in a greater deviation in the cruising course of the boat. Thus, the cruising performance of the boat is varied in accordance with the three-dimensional attitude of the outboard engine 1, so it is difficult for the conventional engine control apparatus to provide for intended good cruising performance desired by the operator at all times.